This invention relates to sintered plastic sheet materials.
Gliding board bases, such as ski and snowboard soles, are typically made of a thermoplastic material, such as polyethylene, and have been made with different areas of the sole having different properties. For example, U.S. Pat. No. 5,310,205 discloses a ski sole having a pair of relatively high hardness strips of polyethylene located near the ski edges in a runner zone and a softer polyethylene material located elsewhere on the ski sole. The patent also indicates that the sole can be obtained by sintering, but states that greater hardness can be obtained by extrusion.
Swiss Patent CH 643463 discloses a block sintering process for forming ski bases having anisotropic properties across the base. The patent describes molding three layers of pulverulent base material in a cylindrical composite compression mold. The base material is sintered under pressure and a continuous strip is skived, or peeled, off from the sintered body. The patent describes that the skived strip may have different areas having different properties depending on the materials used to form the layers and how the strip is skived from the sintered block.
In one embodiment incorporating aspects of the invention, a method for forming a unitary sheet material suitable for use in manufacturing gliding board bases includes placing a first group of materials including plastic particles on a surface in a first pattern, and placing a second group of materials including plastic particles on the surface in a second pattern. Heat and pressure are applied to sinter the plastic particles together to form the unitary sheet material having a first area with a first set of characteristics formed mainly of particles from the first group adjacent a second area with a second set of characteristics different from the first set of characteristics formed mainly from particles from the second group. The first and second sets of characteristics may include only one characteristic, such as color, hardness, wear-resistance, etc., or a plurality of different characteristics.
In another embodiment, a sheet material suitable for forming gliding board bases includes a first area with a first set of characteristics formed mainly from a first group of materials including plastic particles, and a second area with a second set of characteristics different from the first set of characteristics formed mainly from a second group of materials including plastic particles. The plastic particles in the first and second groups of materials are sintered together by a continuous sintering process to form the sheet material.
These and other aspects of the invention will be apparent from the following description and appended claims.